Ore separating devices are well known in the art. Perhaps the most common is the pan or batea (a pan with radial corrugations). Its use and operation is well-known.
The cradle or rocker was an improvement over the pan. An ore-water slurry was dropped onto an apron which distributed the slurry across the riffles, which were pieces of wood or iron perpendicular to the bottom and sides of the cradle. The apparatus was continuously rocked, and as the material moved through the rocker, the gold or heavy metals were caught by the riffles. When enough gold was accumulated, the riffles were cleaned. The riffle is also widely used in sluice boxes and corduroy tables. The name is commonly applied to any strip, bar, or groove placed at right angles to the flowing stream to provide a protective spot where gold can settle. A sluice box is an inclined wooden trough, through which an ore-water slurry stream passes. The gold sinks to the bottom and lodges behind crossbars or riffles in the trough bottom. The corduroy table consists of wide sloping plates with shallow sides which hold a coarse corduroy cloth. Periodically, the corduroy is removed and washed by hand in boxes partly filled with water to recover the gold-rich concentrates. With any of the foregoing apparatuses, additional separation of the retained concentrates, such as by panning, is normally required.
With the exception of panning, which is a slow process, the foregoing apparatuses have recovery efficiencies of only about 60%. The present invention, which also employs riffle separation, produces gold recoveries of 90 to 100% after panning of recovered concentrates.
Separating machines of varying sophistication employing conically-shaped separation surfaces have also been suggested. See U.S. Pat. Nos. 228,125, 382,833, 654,662, 774,048, 1,306,270 and 3,802,916. The present invention employs a conically-shaped separation surface; however, the separation surface and other parts of the apparatus are uniquely configured to maximize recovery and ease of operation.